I've already seen the tutorials to make a cone and be able to unfold it using a 359° revolution and the addition of a fold.
My need is a little more advanced because I would like to obtain the development of a cone BUT with an overlap of the sheet metal to allow the assembly of the cone in spot welding.
You make a normal cone edge to edge and then you add a line to your flat press (a sketch with the necessary roundings + 50mm extrusion necessary for the overlap.)
Then to make the right width depending on whether you make a silk or not.
You should not use the revolution function and then convert to sheet metal but transition fold.
You create the bottom shape and then the top shape of the plane that you will have created before then you use the transition fold sheet metal function as in my last one that I had attached in the previous answer (part teste_02.sldprt) made in SolidWorks 2016
Well if I have no choice, I'll try to do it like this even if it doesn't really suit me;)
I still have a problem though, when I try to reproduce the method of your ac-cobra file, I can't select the 1st sketch... Which seems identical to yours. Any idea??